A catheter is a tubular apparatus for drawing liquid from a body cavity or cavities of organs. A cardiac catheterization is a procedure to insert a flexible catheter into a blood vessel (artery or vein) and reach to heart. The cardiac catheterization is used to inject medicine, measure blood pressure and blood flow of heart and central blood vessel, or diagnose a congenital heart disease. In addition, the procedure is used to investigate a narrowed passage between atrium and ventricle, and abnormal blood flow, or insert electrodes into heart to restore or control heartbeat. A left cardiac catheterization is recently developed and it is a very difficult and dangerous procedure because it is performed by inserting a catheter into artery in opposite direction of blood flow or puncturing interatrial septum; however, it is a very important diagnosing method.
The radiofrequency catheter ablation is a method to treat tachycardia by using electricity. This method is advantageous in that tachycardia can be treated without heart surgery. The radiofrequency catheter ablation is used to treat supraventricular tachycardia with pulse rate exceeding 100 BPM (beats per minute) and some ventricular tachycardia. Especially, it is very efficient to treat paroxysmal supraventricular tachycardia, ventricular tachycardia, atrial fibrillation, and atrial flutter. It has been mostly used to treat paroxysmal supraventricular tachycardia and recently it is increasingly used for atrial fibrillation
The radiofrequency catheter ablation is a method in which radiofrequency electric currents emitted from an electrode catheter located at heart causes local tissue necrosis and finally removes a source area of tachycardia. In this method, when the radiofrequency electric current is released to an especially designed electrode catheter contacting with a lesion to be ablated, the end of the electrode is heated to 60° C.-100° C. and this heat causes heart tissue necrosis, finally removes irregular heartbeat. Specifically, this procedure is done on an empty stomach condition and three or four electrode catheters are inserted into a left or right groin region, accessing a femoral artery or a femoral vein under local anesthesia. An additional electrode catheter may be inserted into subclavian vein, if necessary. Through the electrode catheters, electric stimuli are given to several regions of heart and arrhythmia is caused to diagnose its mechanism and a source area. An injection may be used when arrhythmia is not caused, and the electrotherapy is repeatedly performed changing regions to be treated until source areas of tachycardia are ablated and tachycardia is not caused. Usually, the procedure is done 1-10 times and each procedure takes 3-5 hours. The success rate of treating paroxysmal supraventricular tachycardia is over 90%, and that of treating atrial fibrillation is 70-80%. In 5% of patients, complications such as atrioventricular conduction block, hemopericardium, myocardial infarction, embolism, thrombosis, and hemorrhage may occur. Further, there is a possibility of death. Atrioventricular conduction block can be treated by artificial pacemaker surgery, and embolism and thrombosis can be treated by emergency surgery to remove blood or thrombus. There is a chance to recur in 5% of patients even when the procedure is successfully performed.
The radiofrequency catheter ablation is performed by using a radiofrequency ablation catheter which ablates a source myocardial region of arrhythmia through radiofrequency electric currents. However, conventional radiofrequency ablation catheters create transmural lesions incompletely. Especially, it is so difficult to create a transmural lesion at a thick myocardial region such as left ventricle that the treatment efficiency for ventricular tachycardia or atrial fibrillation is low.